1. Field of the Invention
The invention relates to Campylobacter jejuni gene products and immunogenic fragments of the gene products useful as component(s) of a pharmaceutical formulation capable of eliciting an anti-Campylobacter jejuni immune response. The invention also relates to a method of using inducing an anti-Campylobacter immune response by the administration of C. jejuni-secreted, flagellar gene co-regulated gene products or immunogenic fragments of the gene products.
2. Description of the Related Art
C. jejuni is a leading cause of diarrheal disease worldwide and a documented threat to US military personnel (Taylor, 1992; Tauxe, 1992). The symptoms of Campylobacter enteritis include diarrhea, abdominal pain, and fever and often accompanied by vomiting. Stools usually contain mucus, fecal leukocytes and blood, although watery diarrhea is also observed (Cover and Blaser, 1999). However, despite the importance of this organism to human disease, there are no licensed vaccines against C. jejuni. 
Although Campylobacter infection is treatable with antibiotics, an effective vaccine formulation against the organism is a preferred method for disease prevention. Vaccine administration is especially desirable for travelers to regions of the world where Campylobacter is endemic. However, there are currently no licensed vaccines for this organism. Further hampering efforts in anti-Campylobacter vaccine development is the potential initiation of Guillain-Barre Syndrome (GBS) individuals exposed to Campylobacter (Kuroki, et al, 1991). However, because of the importance of flagellin in Campylobacter virulence, these genes have been promising in the development of anti-Campylobacter immunity (U.S. Pat. No. 6,987,176 to Guerry, et al).
Campylobacter posses a single polar flagella that has been shown to be critical for intestinal colonization and invasion (Wassennar, et al, 1991; Yao, et al, 1994). Flagellin has been shown to be the immunodominant antigen during human and animal infection and is required for colonization in vivo (Guerry, et al, 2000). Flagellar biosynthesis is regulated in a hierarchical fashion with genes expressed in the order in which they are required for the assembly of the flagellum. The production of flagella, however, requires significant expenditure of energy. Therefore, the regulation of these genes is of critical importance to the organism. However, unlike other bacterial species, only three sigma factors have been identified Campylobacter jejuni (σ70, σ54 and σ28) (Parkhill, et al, 2000). These observations suggested that a number of Campylobacter genes are coordinately regulated.
Among members of the family Enterobacteriaceae, the genes flhC and flhD are the initial regulators of the flagellar regulatory cascade (Macnab, 2003). Within this scheme, a feedback mechanism ensures the correct order of flagellar gene expression. In Campylobacter jejuni, which lacks the flhC and flhD regulators, the genes in the flagella regulon expressed intermediate and late in the flagella regulatory cascade are controlled by the sigma factors σ54 and σ28, respectively.
Based on studies using the flhA gene and the gene fliA in the C. jejuni strain NCTC 11168, it has been observed that some genes of unknown functions, but not appearing to be directly involved in flagella function, were also co-regulated along with those genes associated with flagella function (Parkhill, et al, 2000); Carillo, et al, 2004). The flhA gene is expressed early in the cascade and which is involved in export of flagella proteins and the gene fliA encodes σ28. Later studies have shown that many of these genes are also down-regulated in flagella mutants in C. jejuni 81-176, including the gene Cj0977 (Goon, et al, 2006).
The Cj0977 proteins, which are co-regulated with the flagella regulon, are 21.2 kDa and are 98% identical between the C. jejuni strains NCTC 11168 and 81-176 (Goon, et al, 2006). Furthermore, using a Cj0977 mutant, it was shown that Cj0977 resulted in significant attenuation of disease, using the ferret diarrhea disease model. However, the role of Cj0977 in virulence is still not understood. Furthermore, although Cj0977 is clearly important for virulence (Goon, et al, 2006), the protein has not been found to be secreted.
A putative σ28-regulated gene, Cj0859c, encodes a protein with no homology to known proteins, and maps in a region of the chromosome that has been reported in a recent microarray study to be variable among strains (Parker, et al, 2006). Reduced expression of this gene has been shown in a fliA mutant of NCTC 11168 (Carillo, et al, 2004). Analysis of this region in the C. jejuni genomes indicated that the putative σ28 promoter was conserved, but that there was variation in the Cj0859c gene.
There is currently no effective anti-Campylobacter vaccine. Therefore, the identification of new anti-Campylobacter immunogenic formulations is of critical importance.